The invention relates to a directional antenna mechanism of a mobile radio tracking receiver, comprising four antenna elements, which are fastened as articulated to the body of the radio tracking receiver, where the electronic components and devices of the tracking receiver are placed inside the body, and where the antenna elements are turnable to an operating position in which they are pointed away from the body and to a transport position in which they are placed substantially parallel to the direction of the longitudinal axis of the body.
Portable, hand-held radio tracking receivers are often utilized in positioning systems. This positioning method is based on there being a radio transmitter sending a radio signal in the target being positioned. The receiver is used to determine from which direction the radio signal is coming, whereby it is known in which direction the target being positioned is. Radio tracking systems are used, among other things, in various emergency positioning systems, in the positioning of pets and hunting animals and in the positioning of hikers, hunters and inmates of institutions.
The ability of a radio tracking receiver to determine the incoming direction of the radio signal is based on a directional antenna in the receiver. A directional antenna has the basic property that it receives a radio signal well when the antenna is directed straight towards the radio transmitter sending the signal. A signal coming from other directions is attenuated by the directional antenna. The dimensions of the directional antenna depend on the radio frequency used. The antenna used in the mobile tracking receivers on the market today is generally a so-called Yagi antenna with 2 or 3 elements. The directional antenna is often integrated into the same body with the radio receiver in order to create an easy-to-use and small-sized hand-held radio tracking receiver.
Directional antennas generally include four separate, elongated antenna elements, which can be arranged in the body of the radio receiver in many different ways. One way is to fasten the antenna elements at one end as hinged to the body in a way that they can be bent to a operating position, in which the antenna elements are pointed away from the body, and to a transport position, in which the antenna elements are placed in the direction of the body and against it. Turning the hinged antenna elements one by one to the right position manually is a slow procedure. In addition, the antenna elements can remain in a faulty position, in which case the device does not function as intended or it can give incorrect tracking results. There are also prior art devices in which the hinged antenna elements are arranged to open by spring force. However, such a device is inconvenient and even dangerous in use, because when the device is set in the operating position, the antenna elements fling out with great speed. In addition, it is difficult to fold the antenna elements back to the transport position manually, because the spring force pushes the antenna elements into the opposite direction.
The antenna elements can also be telescopic, in which case they are inside the body in the transport position. In the using situation, the antennas are drawn out from the body manually one by one, and therefore the opening of telescope antennas takes place slowly. The antennas can easily remain incompletely drawn to the correct length, in which case the tracking result can become incorrect. In addition, the mechanic durability of telescope antennas is poor.
There is also a prior art mobile radio receiver, in which some of the antenna elements are embedded in the body of the device and some in an openable lid in the device. The device is set ready for operation by opening the lid. Such a radio receiver has to be made relatively large so as to make the antenna elements fit inside the body and the lid in the spread position. In addition, the electronic components of the receiver part in the body of the device are located between the antenna elements, which disturb the operation of the antenna and may cause faulty indications and a deterioration of the receiving ability.
The reference publication GB 371 476 discloses a directional antenna mechanism especially suited for submarines, comprising a pipe-like support part, which is fastened as hinged to the body of the vessel. The reference publication U.S. Pat. No. 3,409,892 discloses a foldable antenna arrangement installed in a vehicle, comprising two transmission antennas and two reception antennas. The solutions described in the above reference publication are large-sized and are thus not suitable for use in small-sized, mobile radio tracking devices.
The purpose of the invention is to disclose a directional antenna mechanism with a new kind of structure, by which the drawbacks and disadvantages related to the prior art directional antennas of the radio tracking receivers can be significantly reduced.